ELLSWORTH AIR FORCE BASE, S.D. — Senior Airman Clayton Luker, 28th Medical Group medical technician, fastens his helmet while donning Mission Oriented Protective Posture gear during the the Phase II Operational Readiness Exercise, May 12. MOPP 4 consists of chemical and biological warfare jackets and pants, protective rubber boots, rubber gloves and gas mask. (U.S. Air Force photo/Senior Airman Adam Grant)